1. Technical Field
The present invention relates to a self-luminous display device and an electronic apparatus including the display device.
2. Related Art
For example, an organic EL device in which pixels having transistors and organic electro-luminescence (hereinafter, referred to as an organic EL) elements are arranged in a matrix shape has been proposed as an example of a display device (JP-A-2012-38677).
In the organic EL device disclosed in JP-A-2012-38677, a reflection layer, a reflection layer protection layer (insulation film), an organic EL element, a protection layer, a color filter, a light-transmitting counter substrate, and the like are laminated in order on a substrate on which transistors are formed. The organic EL element includes a pixel electrode, a light emitting function layer, and a cathode which are laminated in order from a side of the insulation film. The organic EL device has an optical resonance structure in which the optical distance between the reflection layer and the cathode is optimized. Light (red color light, green color light, and blue color light), the color purity of which is increased by the multi-reflection interference of reflected light, passes through color filters and is emitted from the side of the counter substrate as display light. As a result, color display which has excellent color purity is provided.
In the organic EL device disclosed in JP-A-2012-38677, red color light, green color light, and blue color light are extracted from light emitted from the organic EL elements based on the optical resonance structure, and thus it is possible to acquire color display while omitting the color filters and it is possible to increase the brightness of display by omitting the color filters.
However, when the color filters are omitted from the organic EL device disclosed in JP-A-2012-38677, some of light emitted from the organic EL elements is reflected between the counter substrate and the reflection layer, and thus there is a problem in that display qualities are deteriorated.
Hereinafter, the details will be described with reference to FIGS. 11 to 12B.
FIG. 11 is a schematic diagram illustrating an organic EL device according to a well-known technology. FIGS. 12A and 12B are typical cross-sectional diagrams taken along line XII-XII of FIG. 11. In FIG. 12A, the state of light emitted from the organic EL elements is schematically illustrated. In FIG. 12B, a state of light corresponding to a display of FIG. 11 is schematically illustrated.
An organic EL device 500 includes a structure in which a color filter layer is omitted from the organic EL device disclosed in JP-A-2012-38677. As illustrated in FIG. 11, the organic EL device 500 includes an element substrate 510 and a counter substrate 530 which is arranged to face the element substrate 510. The counter substrate 530 is formed of, for example, glass, and has transparency. The refractive index n1 of the counter substrate 530 is 1.46.
The organic EL device 500 includes a display area V in which a plurality of pixels are arranged. There is a case in which, when a pattern 551 is displayed in an area Z1 of the display area V, a pattern 552 is displayed in an area Z2 which is separated from the area Z1, and a pattern 553 is displayed in an area Z3 which is separated from the area Z2.
Hereinafter, it is assumed that a direction along the long side of the element substrate 510 is an X direction, a direction along the short side of the element substrate 510 is a Y direction, and a direction which faces the counter substrate 530 from the substrate 510 is a Z direction.
Initially, the structure of the organic EL device 500 and the state of light which is emitted from the organic EL device 500 will be described with reference to FIG. 12A.
As shown in FIG. 12A, in the organic EL device 500, the element substrate 510, a resin layer 520, and the counter substrate 530 are sequentially arranged in the Z direction. The resin layer 520 is formed of, for example, an epoxy resin, and bonds the element substrate 510 to the counter substrate 530.
The air 601 is arranged on a surface 530a which is an opposite side of a surface of the counter substrate 530 which faces the element substrate 510. The refractive index n2 of the air 601 is approximately 1.
The element substrate 510 includes a substrate 511, a reflection layer 512, a reflection layer protection layer (insulation film) 512a, an organic EL element 513, and a protection film 514 which are sequentially arranged on the substrate 511 in the Z direction. A transistor (not shown in the drawing) which drives the organic EL element 513, a drive circuit (not shown in the drawing), and the like are formed on the substrate 511. The protection film 514 is a passivation film which suppresses the deterioration of the organic EL element 513 and has transparency. The reflection layer 512, the insulation film 512a, and the organic EL element 513 form the optical resonance structure. Red color light, green color light, and blue color light, which are emitted from the light emission layer of the organic EL element 513 and the color purities of which are increased by the multi-reflection interference of the reflected light in the optical resonance structure, are emitted in the Z direction as the display light.
Light LB1, which is emitted from the light emission layer of the organic EL element 513 and the color purity of which is increased by the optical resonance structure, is incident to the surface 530a of the counter substrate 530. Some of the light LB1 are reflected in the boundary surface (surface 530a) between the counter substrate 530 and the air 601 and are ejected on the side of the air 601 as light LB2. Some of the light LB1 are reflected in the surface 530a and are progressed on the side of the reflection layer 512 as light LB3.
Hereinafter, the light LB1 is called incident light LB1, the light LB2 is called refracted light LB2, and the light LB3 is called reflected light LB3.
When it is assumed that an angle generated between the incident light LB1 and the normal vector (Z direction) of the surface 530a is set to θ1 and an angle generated between the progress direction of the refracted light LB2 and the Z direction is set to θ2, Expression (1) described below is realized based on Snell's law.n1 sin θ1=n2 sin θ2  (1)
The angle θ1 generated between the progress direction of the incident light LB1 and the Z direction based on Expression (1) is expressed using Expression (2) described below.θ1=sin−1((n2 sin θ2)/n1)  (2)
A condition in which the angle θ2 generated between the progress direction of the refracted light LB2 and the Z direction is greater than 90° corresponds to a condition in which the incident light LB1 does not progress at the side of the air 601, that is, a condition in which all of the incident light LB1 are reflected in the surface 530a. Therefore, the angle θ1 acquired when the angle θ2 is 90° is a critical angle α at which the incident light LB1 is totally reflected in the surface 530a. 
When the angle θ1 generated between the progress direction of the incident light LB1 and the Z direction is less than the critical angle α, the incident light LB1 is divided into the refracted light LB2 and the reflected light LB3 in the surface 530a. When the angle θ1 generated between the progress direction of the incident light LB1 and the Z direction is equal to or greater than the critical angle α, the incident light LB1 is totally reflected in the surface 530a and becomes the reflected light LB3. Therefore, when the angle θ1 generated between the progress direction of the incident light LB1 and the Z direction is equal to or greater than the critical angle α, the brightness of the reflected light LB3 is the highest.
In contrast, the wavelength of light which is amplified by the above-described optical resonance structure changes according to the direction of light which passes through the optical resonance structure. More specifically, with regard to light which passes through the optical resonance structure in an oblique direction (direction perpendicular to the Z direction), the intensity of light on a short wavelength side increases compared to the light which passes through the optical resonance structure in the Z direction. Therefore, when the angle θ1 generated between the progress direction of the incident light LB1 and the Z direction becomes large, the wavelength of enhanced light changes to a short wavelength side. For example, when the intensity of light in a blue color wavelength region increases under a condition that the angle θ1 based on the Z direction is 0°, the intensity of light on a short wavelength side rather than the blue color wavelength region, that is, light in a wavelength region which is difficult to be recognized by human eyes increases under a condition that the angle θ1 based on the Z direction is greater than 0°.
That is, when the angle θ1 generated between the progress direction of the incident light LB1 and the Z direction is greater than the critical angle α, the wavelength of the incident light LB1 which is enhanced by the optical resonance structure changes to the short wavelength side, and thus it is difficult to be recognized by human eyes. Therefore, the incident light LB1 under the condition that an angle based on the Z direction is the critical angle α is easily recognized by human eyes and is easily conspicuous rather than the incident light LB1 under the condition that the angle based on the Z direction is greater than the critical angle α. Therefore, the incident light LB1 under the condition that the angle based on the Z direction is the critical angle α affects the display of the above-described pattern 552 and the pattern 553 most.
Subsequently, a cause of the display of the pattern 552 and the pattern 553 subsequent to the display of the necessary pattern 551 will be described with reference to FIG. 12B. In addition, it is assumed that light M1, M2, and M3 ejected in the Z direction are viewed as display light in the drawing.
As shown in FIG. 12B, the light M1 is ejected in the Z direction from the organic EL element 513 in the area Z1, and thus the necessary pattern 551 is displayed.
Light in a direction which is perpendicular to the Z direction is also ejected from the organic EL element 513 in the area Z1 other than the light M1 in the Z direction. From among light ejected in the direction which is perpendicular to the Z direction, the incident light LB1 in which the angle based on the Z direction is the critical angle α is totally reflected in the surface 530a and faces the side of the reflection layer 513 as the reflected light LB3.
The reflected light LB3 progresses to the side of the reflection layer 512 and is reflected in the reflection layer 512 of the area Z2. The reflection layer 512, which is formed on the substrate 511 on which transistors, drive circuits, and the like are formed, includes various types of unevenness, and the reflected light LB3 is reflected in various directions. The pattern 552 is formed by the light M2 in the Z direction from among light reflected in the reflection layer 512 of the area Z2.
Further, from among light reflected in the reflection layer 512 of the area Z2, incident light LB1a, in which the angle based on the Z direction is in the vicinity of the critical angle α, progresses to the side of the surface 530a, is totally reflected in the surface 530a, and progresses to the side of the reflection layer 513 as reflected light LB3a. The reflected light LB3a is reflected in the reflection layer 512 of the area Z3. The pattern 553 is displayed by the light M3 which faces the Z direction from among light reflected in the reflection layer 512 of the area Z3.
Further, the display states of the pattern 552 and the pattern 553 change according to the directivity of light reflected in the reflection layer 512 (the reflection performance of the reflection layer 512).
For example, when light is reflected in the reflection layer 512 in the X direction, the pattern 552 and the pattern 553 are displayed after being arranged in the X direction as shown in FIG. 11. For example, when light is reflected in the reflection layer 512 in the Y direction, the pattern 552 and the pattern 553 are displayed after being arranged in the Y direction. For example, when light is reflected in the reflection layer 512 in a direction (oblique direction) which is perpendicular to the X direction and the Y direction, the pattern 552 and the pattern 553 are displayed after being arranged in the oblique direction. For example, when light is reflected in the reflection layer 512 while being spread in the X direction, the pattern 552 and the pattern 553 are displayed in a wide range compared to the display state shown in FIG. 11.
For example, when the reflection layer 512 is flat and light is not reflected in the reflection layer 512 in the Z direction, the pattern 552 and the pattern 553 are not displayed. For example, when light is uniformly reflected in the reflection layer 512 in all of the directions, the intensity of light which is reflected in the Z direction is weak, and thus it is difficult for the pattern 552 and the pattern 553 to be conspicuous.
Since the reflection layer 512 is formed on the substrate 511 on which the transistors, the drive circuits, and the like are formed, that is, on the substrate 511 which includes various types of unevenness, it is difficult to control the reflection performance of the reflection layer 512 (the surface unevenness of the reflection layer 512). Therefore, in the organic EL device 500, when the necessary pattern 551 is displayed in such a way that light is reflected in the reflection layer 512 in a specific direction (Z direction), there is a problem in that the pattern 552 and the pattern 553 are displayed.